US forces training in Kuwait were caught up in the fourth shooting incident in less than a month, according to a US spokesman at Camp Doha."Shots were fired in the vicinity of the area where the soldiers are located in the south," the spokesman told AFP on Saturday.

The incident occurred Friday in Orayfijan, some 60 kilometers (37 miles) south of Kuwait City, at approximately 7:30 am (0430 GMT).

The soldiers saw "two white pick-up trucks. They were sure the two trucks fired the shots, which were fired in the vicinity of the soldiers," the spokesman said, adding that fire was not returned.

The soldiers were engaged "in support of training going on for Operation Desert Spring," an ongoing joint exercise with Kuwaiti forces, the spokesperson said.

They were not in vehicles at the time the shots were fired and no injuries were reported.

The incident is being investigated by Kuwaiti security authorities, the spokesman added.

A US marine was killed and another injured on October 8 when attacked by two Kuwaitis while conducting wargames on Failaka island, 20 kilometers (12 miles) east of Kuwait City.

A day later, US forces opened fire on a vehicle whose occupants "drew a weapon and pointed it at" US troops in a Humvee all-terrain vehicle who were heading to their training area north of Kuwait City.

Five days later, the US embassy here said shots were fired from two unidentified civilian sports utility vehicles at US military units near a northern Kuwait training area. There were no injuries.

While condemning the Failaka shooting as a "terrorist" act, the Kuwaiti authorities played down the two shooting incidents that followed.

One of the two assailants gunned down in the Failaka shooting had sworn allegiance to al-Qaeda chief Osama bin Laden, Interior Minister Sheikh Mohammad Khaled al-Sabah has said.

Six Kuwaitis are being questioned in connection with the deadly attack.

The suspects formed an "organization" that was planning to strike at five other US and foreign targets, the minister said.

US Federal Bureau of Investigation agents are currently in the emirate following up on the Failaka attack and probing possible security lapses.

As of Saturday, Kuwait is restricting access to the entire northwestern part of the emirate, one quarter of the country, in what it described as a precaution during continuing joint Kuwaiti-American military exercises.

Some 10,000 US troops are based here and regularly conduct joint maneuvers with the Kuwaiti armed forces in line with a defense pact signed after a US-led coalition launched the 1991 Gulf War that liberated Kuwait from Iraqi occupation.

Camp Doha is some 30 kilometers (18 miles) north of Kuwait City.

PHOTO CAPTION

American vehicles cross the 'military zone' in Abdaly